A system for rotating the arm of a forging manipulator is known, this system uses an electric motor, a slip clutch and a reduction gear. The change in direction of rotation of the arm is effected by reversing the electric motor. This system does not permit any change in the velocity of rotation of the armor a smooth starting and stopping. For this reason, such drives are very rarely found in contemporary forging manipulators.
In another system the rotation of the arm is effected by means of an electric motor and a special variable speed gear drive structure (normally the gear drive is planetary, and in the case of (e.g. a differential). This system, too, does not permit any change in the velocity of rotation, while being expensive and requiring a complex epicyclic toothed wheel.
In yet another system a double-acting hydraulic cylinder, a toothed rack, a toothed wheel and a compound gear drive with hydraulic switching, reverses automatically the direction of rotation of the arm during the back stroke of the rack. This system is very complex and expensive and increases the dimensions of the manipulator in a horizontal plane.
Still another system makes use of eight hydraulic cylinders, four toothed racks, four toothed wheels and four free-wheeling clutches. This system, too, is very complex and expensive and increases the horizontal dimensions of the manipulator.
Finally a prior-art system comprises a hydromotor and a gear drive. It is at the present the most widespread in use, although it is comparatively complex and expensive.